It needs no introduction, just click, and stare.
If you keep watching, it will go through several different photos. Then it starts repeating itself, going through the same photos over and over again. But you may want to keep watching, because it will do different effects (sometimes making the photos clearer, sometimes fuzzier), and so it never really stops changing.
Basically how it works, you go here and type anything into the box. It does a Google image search, and finds the photos. Then does it's own thing with them. It's really rather neat, and I've just wasted almost an hour staring at it.